Could life exist in the clouds of distant planets? This research delves into the critical question of nutrient availability within the atmospheres of rocky exoplanets, exploring the potential for aerial biospheres. The study introduces a framework for assessing nutrient levels based on the presence of water condensates and the chemical states of key elements like carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur (CHNOPS). Applying this framework to various atmospheric models, the research examines how planetary surface compositions influence atmospheric chemistry and nutrient distribution. The models incorporate atmosphere-crust interactions and element depletion due to cloud formation. Key findings reveal that while reduced forms of carbon, nitrogen, and sulfur are often present at the water cloud base, phosphorus and essential metals are frequently lacking. This suggests that carbon, nitrogen, and sulfur may be bioavailable, but the absence of phosphorus and metals could significantly limit the development of aerial biospheres. The study highlights the need for further research into the mechanisms of phosphorus and metal transport in exoplanetary atmospheres to fully understand the constraints on extraterrestrial habitability. This framework advances our understanding of the factors shaping the potential for life beyond Earth, linking planetary geology to atmospheric chemistry and biological possibility. Future studies could build on this framework by incorporating more complex atmospheric processes and considering a wider range of planetary conditions.
Published in the International Journal of Astrobiology, this paper directly aligns with the journal's focus on the origin, evolution, distribution, and future of life in the universe. By exploring the habitability constraints related to nutrient availability on rocky exoplanets, the research complements the journal's existing body of work on exoplanetary environments and the conditions necessary for life beyond Earth.